MAWP of 316/316L Dual-Marked Flanges?

[KernOily]

Hi guys. I received an interesting question today and I think I know the answer but I want to hear what you think.

For a P2.2/P2.3 material ASME B16.5 flange that is dual-marked as 316/316L, what would you use as the allowable stress at, say, 200° F? The problem is the two materials have different MAWP's. At 200 F, 316 has MAWP of 240 psig and 316L has MAWP of 195 psig.

I am not aware if the B31 Codes address this question.

What say ye? Thanks guys!

 

[XL83NL]

Use the MAWP of 316. Refer to ASME II-D, mandatory appendix 7, article 7-210 for more details.
It's quite common and happens more often (e.g. 304(L))

 

[Duwe6]

What the "316/316L" is telling you is that this alloy batch [heat] meets the mechanical testing minimums for full-strength 316(plain) AND has sufficiently low carbon content to also meet the limited carbon requirement of 316L. If your parts are made of dual-certified stainless - 3xx/3xxL - make sure that this is noted in the design calc's. You gain about 10% strength [thus 10% more 'effective thickness'] while maintaining the improved corrosion and welding characteristics of Low-carbon.